What are disadvantages of aerobic digestion?

• A. Low aeration costs and excellent dewatering.
• B. Odorless product.
• C. Simple operation and low energy use.
• D. High aeration costs and poor dewatering characteristics.

Answer: (D)

Aerobic digestion relies on keeping microbes oxygenated, so you must continuously supply air to the reactor. That makes aeration the dominant operating cost, since large blowers and diffusers must run constantly to meet the oxygen demand. In addition, the solids produced under aerobic conditions tend to have higher moisture content and poorer settleability, which leads to more challenging and energy-intensive dewatering compared with other sludge stabilization methods. Because no methane or other biogas is generated to recover energy, there’s also a missed opportunity for energy production that anaerobic processes offer. Taken together, the downsides are high aeration costs and poor dewatering characteristics.